Having already come from a set down to beat Slam champ Sam Stosur and former World No. 1 Caroline Wozniacki, this time Ostapenko rebounded from losing the second set against 2015 semifinalist Timea Bacsinszky to win 7-6 (4), 3-6, 6-3, a win that improbably took place on both of their birthdays.
Halep showed the full extent of her defensive skills to beat Pliskova and reach her second French Open final. She is now ranked fourth in the world behind Angelique Kerber, Serena Williams and Pliskova.
There's a great deal on the line for Halep in Saturday's final. I have the mentality to win, but it's going to be tough. "I take on a young player, it will be an interesting challenge".
The second-seeded Czech hit 24 unforced errors as Halep took the opener 6-4. Pliskova had a resilient match, battling back from deficits throughout, but Halep ultimately proved to be too much, taking the match 6-4 3-6 6-3. Kuerten won that title - the first of his three French Opens - on June 8, the day Ostapenko was born.
In the end, she could at least reflect on progress in Paris - before this year, she had never got beyond the second round in five attempts.
"I m really happy to be in the final, especially on my birthday".
"I'm really happy, I can't believe it", the 19-year-old Ostapenko said.
However, Ostapenko played fearlessly in the decider and pounded away a 50th clean victor to become the first Latvian player to reach a Grand Slam final. Halep goes into the final as favorite against the tournament's revelation, 20-years old Latvian Jelena Ostapenko.
"But then, like, first match was a tough match and I won it and it kind of gave me confidence".
".I don't think it's better, but somehow I'm just winning".
Ostapenko then broke early in the second set but Bacsinszky won the last four games and levelled the match when her opponent double faulted.
Ostapenko will now try to win the first senior title of her career, and history might just be on her side.
"I think more about the game, and I play smarter, in my opinion, and also physically".
Pliskova was gasping for air after the longer points, but saved three break-back points in the next game and another forehand victor ensured both semi-finals would go the distance.
"Of course I m disappointed".
Bacsinszky - whose birthday was also Thursday; she turned 28 - employed all manner of strategies in a bid to throw off her opponent.
"It's nice to be back in the finals, I hope this time I can play better". After digging her big hole, Halep climbed out by making an effort to drive balls deeper in the court and trying to make Svitolina move more.